Terahertz waves feature unique properties. They pass through many non-conducting materials, including paper, cardboard, plastics, wood, ceramics and composite structures. This opens up a wide field of applications in quality and process control, taking advantage of novel measurement techniques that are inherently safe, fast and contact-free. Inspection systems work either in transmission or reflection, depending on the measurement task.

A promising application is quality control of folded cardboard boxes that are used for pharmaceuticals. European legislation dictates that pharmaceuticals may only be sold with patient information leaflets enclosed. In proof-of-principle measurements, TOPTICA’s researchers have shown that the presence, or absence, of a package insert could be detected unambiguously even for samples moving at more than 20 meters per second.

Fast terahertz systems also lend themselves to the observation of dynamic processes, such as drying or curing of materials. The temporal resolution can even be shorter than 1 µs.